Field of the Invention
The present invention relates to a new and useful knitting machine which uses an electromagnetic needle selection.
Knitting machines or devices of the type having electromagnetic needle selection are already known as part of the state of the art.
Swiss Pat. No. 618,484 describes a knitting machine in which the needles are extended by two superimposed arms (stems), one of which, flexible and fitted with a butt, can be imbedded and held so imbedded by means of an electromagnetic selection for the purpose of placing the needle in out-of-action position in the row in progress, or imbedded temporarily by placing into action one or several pressing devices on one or several of the tracks formed by the alignment of the butts of manually preselected tuck selectors for the purpose of stitch tucking. Even if this solution is fully satisfactory from the viewpoints of design and use, it must be noted that so-called "three-track" knitting, i.e. formation, tucking and out-of-action in one and the same row and one and the same knitting system is limited, for each item, to combinations resulting from the manual distribution of the butts of the tuck selector in either of said tracks.
To increase combination possibilities by using the same system would be tantamount to increasing the number of tracks. Such a modification would result in drawbacks such as the broadening of the cam-holder, the lengthening of the needles and of the needle grooves, an increased number of vertical cams, an increased number of control members for the vertical cams, and a programming complexity making it unsuitable for consideration.
To obtain a possibility of full "three-track" selection with this system, i.e. to select each needle independently of each other in each knitting system and in each row, would make it necessary for the builder to provide one track per needle housed in the bed for each knitting system. Hence, it is physically impossible to extend the system.
German Pat. No. 19 62 787 describes a knitting machine in which the plates are integral with the needles via a ball and socket joint. Several plate-pressing blocks are housed in the same groove as the needle. They make it possible to imbed the needle butts in some spots, so that the butts may be positioned out of reach of the cam boxes.
The plurality of plate-pressing blocks and the wrought shape of the bed constitute major drawbacks with regard to overall dimensions and manufacture. Full "three-track" knitting is not possible without the use of two selection stations, one downstream the knitting system, the other downstream the maximum ascension ramp of a needle viewed in the direction of movement of the selection members with respect to the knitting system; the system's design would be too complicated.
German patent application No. 21 55 251 describes a selection device for the knitting needle selectors making it possible for the needles to be controlled in action position, tuck position and out-of-action position. The selectors may be located in three distinct positions. Two end positions are obtained via electromagnetic selection and deflection of the selectors. A third, intermediary position is obtained by defiling, without deflection, the selector in the selection station. Stabilization of the selector is obtained by means of magnets located below the selection members. The selectors defiling in this third position are held mechanically in this position by means of a stationary channel.
The design of the device, i.e. deflection ramps followed by separate channels representing the three tracks, results in a device that can operate in only one direction and, therefore, is intended for circular knitting machines, for example. A symmetrical embodiment is not possible. An application to linear knitting machines would require two devices arranged so as to operate one in a direction of movement of the knitting carriage, the other working in the opposite direction. Consequently, this solution leads to over-dimensioning of the cam holders.
Swiss Pat. No. 622,566 describes an electromagnetic needle selection device of a knitting machine. A pair of electromagnets acting in opposition to one another form a channel in which selection members defile. The device is symmetrical with respect to the defilement pin of the selection members and symmetrical with respect to the plane of the pair of electromagnets passing through the selection poles. This device is designed to be operational in both directions of movement of a knitting carriage on a linear machine. It defines two distinct positions of the selection members depending on whether one or the other electromagnet is energized. This solution is very satisfactory and fulfills its task even at the high knitting speeds which knitters customarily use.
The drawback of this system, when applied to make selections in accordance with the "three-track" method, is the uncertainty of the position of the selection member in the event that none of the electromagnets is energized.